<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    ul {
      border: 1px solid red;
    }
    li {
      background-color: pink;
    }
  </style>
</head>
<body>
  <ul>
    <li>123</li>
    <li>456</li>
  </ul>
  
  <script>
    var ul = document.querySelector('ul')

    ul.addEventListener('click', function(e) {
      console.log( this )  // 谁调用 this 指向谁  ul
      
      console.log( e.currentTarget )  // ul 事件绑定给谁，我们指向谁

      console.log( e.target )  // 谁 触发 事件， 就指向谁


    })
  </script>
</body>
</html>